The present invention relates to a mask for image formation which has high durability and which is easy to handle.
There is a kind of photographic print on which an image is printed overlaid with a mask which has illustrative pattern concurrently when an image is printed on the photographic paper from a negative film. The aforementioned mask for image formation is made in this manner:
A thermal transfer material having an opaque layer which is impermeable to light, and an image receiving sheet which is permeable to light, are overlapped on each other. Characters or figures are thermally transferred onto the image receiving sheet with a thermal head in such a manner that an opaque pattern is formed on the image receiving sheet. After the transferring of the image has been conducted, the thermal transfer material is peeled off from the image receiving sheet.
When a mask for image formation is made through the aforementioned thermal transfer system, much attention is needed to handle the mask because the opaque pattern is thin and lacks strength, which is one of the problems of a thermal transfer system. When the mask is composed of multi-layers, the adhesive strength between the layers is low in the case where the resilience of an intermediate layer is not sufficient. In particular, when the image receiving sheet is made of a plastic film, its surface is smooth, hard and does not absorb the thermal transfer material so that the opaque pattern can not be tightly fixed onto the film. As the strength of the mask is insufficient as described above, when the mask for image formation contacts or rubs against a hard object, the mask is easily damaged.
In order to take measures to solve these problems, it can be considered to protect the mask with a laminate layer. However, the following problems are caused in this case: When the laminate layer is formed on the mask at a high temperature, the opaque pattern can melt, and the image is damaged. On the other hand, when the laminate layer is formed on the mask at a low temperature, the adhesive strength of the laminate layer is not sufficient. Further, when there is no overcoat layer, the adhesive strength is low.